In an effort to reduce the use of highly enriched uranium fuels, different programs exist to convert research reactors fueled with highly enriched uranium into those fueled by low enriched uranium. The United States Highly Enriched Uranium Reactor Conversion program used to be known as the Reduced Enrichment for Research and Test Reactors program, and it is still known as such internationally. There remains a strong emphasis in converting research reactors fueled with highly enriched uranium into those fueled by low enriched uranium. The highly enriched uranium fuel is made of aluminide, oxide, or silicide particulate dispersed in an aluminum powder and clad with aluminum. The uranium loading densities range from 2 to 5 gU/cm3. Conversion to a low enriched uranium fuel, where there is less than 20% U-235, without impacting reactor performance requires a higher uranium loading density. 15.3 gU/cm3 is achievable within a monolithic U—Mo fuel. Current methods to recover uranium from high-enriched fuel use an aqueous process. During this process, the presence of uranium in combination with zirconium in monolithic uranium fuel introduces explosion hazards.
The projected demand for monolithic low enriched uranium fuel within the U.S. is approximately 1,800 kg annually. Accounting for uranium losses during fabrication indicates an additional 3,000 kg monolithic low enriched uranium fuel would be required annually to meet projected demands. The used fuel and fabrication scrap are of sufficient U-235 enrichment to warrant recovery and reuse of the low enriched-uranium. Due to the high demand of low enriched uranium needed and the safety concerns associated with the aqueous process, there exists a need for a safe processing method of monolithic fuel that can meet the demand that is needed.